Lots of good advice above. You will definitely need to have insurance, but the good news is that boat insurance is generally much less expensive than comparable home owner's or car insurance.
If you are planning on Chartering the boat, insurance is more expensive due to the increased liability, but can be offset by tax savings. Many large yacht owners in my area have their boats available for bareboat charter (with or without a captain). That essentially allows them to write off the bulk of the cost of maintaining their boats as a business expense. Maintaining a yacht in charter ready condition is usually a large expense, and those boats are typically professionally maintained as part of a Charter Fleet. In other words, the owners only use them a few weeks out of the year.
I also know owners that do occasional dinner cruises and such to offset costs, but it is very difficult to both live aboard a boat and make it available for charters.
If you live aboard full time, you tend to accumulate a lot of "stuff" on board that make the boat hard to charter. In other words, the boat tends to look more lived in than charter-ready.
Living aboard is a great experience and I highly recommend it. I would suggest putting the charter idea on a back burner until you get some time with the new boat and have a full understanding of what it costs and takes to maintain and operate it.
I'm curious as to where the boat might be located and what size boat you were thinking of?